The Baltimore Longitudinal Study of Aging (BLSA) has been active for nearly 60 years and represents one of the longest ongoing longitudinal studies of aging ever conducted. The main focus is to describe physiological parameters and longitudinal trajectories of change in these parameters in participants of different ages, initially free of major diseases at the time of enrollment with the underlying goal to discriminate changes due to ?normal aging? from those generated by age-associated conditions. A major threat to achieving this objective is loss to follow-up of the most sick and frail, a phenomenon known as ?informative censoring?. In short, participants who become ill, cognitively impaired or disabled or are admitted to a long-term care facility are less likely to return for their next scheduled visit. Unfortunately, those who cannot participate in the follow-up are also potentially the most informative in terms of health-related outcomes. When information on the most debilitated participants is unavailable, the true downward trajectories of the aging phenotypes may be severely underestimated. The availability of alternative modes of assessment thorough the BLSA Home Visit Program largely eliminates this threat to study validity.